1. Field of the Invention
The invention relates to control panel systems; and more particularly, to a control panel system which employs optical coupling between a light sensitive probe and light emitting means on the panel to select and change switch states.
2. Description of the Prior Art
Electrical systems which are to be controlled by an operator, have traditionally employed control panels, having mechanical switches for manipulation by an operator in a predetermined fashion, for changing the state of associated electrical circuits. Such mechanical switches not only provide the operator with a mechanical and visual interface with the system; but also, serve to inform the operator as to the present controlled state of the electrical system. Incandescent or neon lights, cathode ray tubes (CRT's), and light emitting diodes (LED's), for example, have been employed to display switch or control states and other information to the operator, such as the condition of a particular circuit, and whether the change of state desired by the operator has actually taken place. The number of switches and displays which could be installed on such a conventional control panel has been limited by the physical size and spacing of its components.
With the availability of standard commercially available light emitting and light sensitive diodes, it is possible to change the state of a circuit by optical coupling to perform the functions heretofore performed by mechanical switches.
Heretofore, hand-held light sensitive devices have been proposed to operate in cooperation with a control panel CRT and LED display systems to allow the operator to select (or address) a control input to the system without the need for a mechanical interface at each control location. However, as far as is known, previously proposed, optical coupling control panel systems have presented problems in reliability and ease and certainty of operation which are not present in mechanical switching systems. For example, extraneous light can result in inadvertent switch operation. A loss of power can destroy the states of the various switches. The active act of coupling can prevent operator observance of the change of state. The operator can inadvertently operate a switch easily to an undesired state. Thus, it is desirable to provide a control panel system utilizing all of the advantages of a solid state control system as compared to a conventional mechanical type control panel, while still maintaining the reliability, and ease and certainty of operation of conventional mechanical switch type control panel systems. Also, it is desirable to provide such a system which provides versatility of operation, has low power requirements, and provides compactness of display, which, in many instances, are not practicable for conventional systems.